Do multiple vaccines overload the immune system? Apparently not.

(This post was originally posted on the Good Enough Mum blog, here.)

One common claim of the anti-vaccine movement is that there are just too many vaccines these days, and that the sheer number given is overwhelming the immune systems of many children and leading to all sorts of potential ills specified or unspecified (autism is a biggie here, but there are others attributed as well).  Hence, the whole theory of ‘selective vaccination’, where you pick particular ones to give your children and leave the rest.

I never found this theory terribly convincing.  After all, we’re swimming in germs all the time – the vaccines we get are a tiny fraction of the bacteria and viruses that our immune systems have to deal with on a day-to-day basis, even before you take into account the fact that the germs in vaccines have been deliberately weakened or even killed off before being administered to people.  It always seemed to me like plain common sense that our immune systems wouldn’t find it that much of a big deal to handle several vaccines at a time.  However, I never had anything more concrete than that to counter the claims about overloading of the immune system.

Then, I read Paul Offit’s “Autism’s False Prophets“.  This is the book I have been hoping for years that somebody would write; a clear and simple account by a paediatric microbiologist of the whole story of the vaccine/autism controversy, giving the true stories behind the many frightening and plausible-sounding claims made by the anti-vaccine campaigners and explaining why the evidence does not support them.  The debunking of conspiracy claims was marvellously welcome; the scientific parts of it, of course, I already knew quite a bit about because of having access to medical journals. But I learned one particular piece of information that I actually hadn’t known and that sounded so simple and obvious once it was explained that I still can’t believe it isn’t publicised far more by the pro-vaccine side of the argument; the scientific reason why the ‘overloading the immune system’ theory doesn’t stand up.  I share it with you here in honour of National Vaccines Week.

You see, although we think of vaccines in terms of how many germs are vaccinated against (and thus it looks to us as though the list is getting longer and longer; and, while I don’t see that as a problem for the reason given above, I can appreciate that to a lot of parents it does look daunting), that isn’t how it works on the level of the immune system.  The immune system ‘sees’ things in terms of how many proteins it has to mount an antibody response to.  And this is not a simple one-to-one relationship; in fact, every germ that the immune system mounts defences against has multiple surface proteins against which antibodies need to be made.  The number of proteins involved (they’re called antigens, by the way, if you want the technical term) depends partly on the size of the virus or bacterium being fought against; in the case of vaccines, I believe it also depends partly on the technique used to render the germ in question unable to cause full-blown infection so that it can be safely injected into the human body.  (When Offit made this point, I did in fact remember something I’d seen mentioned in passing during the huge controversy over the five-in-one vaccine that was brought in a few years ago; that it actually contained fewer of these proteins than the separate vaccines had, and was thus, if anything, going to present less of a challenge to the immune system than the vaccines given prior to that.)

Anyway, about a hundred years ago or thereabouts, the only vaccine children received was the smallpox vaccine; now, of course, they receive far more than that.  But, according to Offit, the number of foreign proteins presented to a child’s immune system by the total vaccination schedule currently recommended for children in the United States today is actually substantially less than the number of foreign proteins that were contained in the smallpox vaccine alone.  (Here in the UK, of course, it will presumably be even fewer, as there are a couple of vaccines on the US schedule that we don’t have on ours.)  The smallpox vaccine (which is no longer given) contained a grand total of 200 foreign proteins for the immune system to deal with in one go; the vaccines advised for a child in the US today contain a somewhat more petite total of 153 foreign proteins.  So, if overloading of children’s immune systems from vaccines actually was the cause of autism or of whatever disease the anti-vaccine lobby happen to be currently claiming, we’d expect to see the rate of the disease in question dropping rather than rising.

The logical conclusion?  No, the current vaccine schedule is not causing any sort of overload of children’s immune systems.  Children’s immune systems, in fact, have noticeably less to deal with than they did a hundred years ago.  153 proteins?  Luxury.